Example: confidence

Selection and integration of high temperature catalysts ...

Project ERA-NET Bioenergy Stove 2020 Workshop: Wood Stoves 2020 - Towards high efficiency and low emissions Stockholm (Sweden), 13th of June 2017 Selection and integration of high temperature catalysts into a stove Thomas Brunner, Christoph Mandl, Ingwald Obernberger Contents Background and objectives catalysts for wood stoves Methodology high temperature catalysts applied Description of the chimney stove and the test stand Test run procedure Results of the test runs performed Metal based catalyst Foam ceramic catalyst Conclusions and recommendations 2 Background and objectives (I) In the recent 15 years biomass based room heating systems became more and more popular and the development towards low emission appliances is progressing. In particular, a further development and optimisation of stoves is necessary in order to achieve low emissions of atmospheric pollutants and particularly to meet stricter emission limits. Secondary measures like oxidation catalysts are already applied for emission reduction of wood stoves.

Background and objectives (I) In the recent 15 years biomass based room heating systems became more and more popular and the development towards low emission appliances is progressing. In particular, a further development and optimisation of stoves is necessary in …

Tags:

  High, Selection, Temperatures, Integration, Catalysts, Selection and integration of high temperature catalysts

Information

Domain:

Source:

Link to this page:

Please notify us if you found a problem with this document:

Other abuse

Transcription of Selection and integration of high temperature catalysts ...

1 Project ERA-NET Bioenergy Stove 2020 Workshop: Wood Stoves 2020 - Towards high efficiency and low emissions Stockholm (Sweden), 13th of June 2017 Selection and integration of high temperature catalysts into a stove Thomas Brunner, Christoph Mandl, Ingwald Obernberger Contents Background and objectives catalysts for wood stoves Methodology high temperature catalysts applied Description of the chimney stove and the test stand Test run procedure Results of the test runs performed Metal based catalyst Foam ceramic catalyst Conclusions and recommendations 2 Background and objectives (I) In the recent 15 years biomass based room heating systems became more and more popular and the development towards low emission appliances is progressing. In particular, a further development and optimisation of stoves is necessary in order to achieve low emissions of atmospheric pollutants and particularly to meet stricter emission limits. Secondary measures like oxidation catalysts are already applied for emission reduction of wood stoves.

2 As these catalysts are usually installed in the flue gas duct down-stream the stove the emission reduction potential is limited due to: The comparably low temperatures at stove outlet The expected slow heat-up of the catalyst at this position. Almost no emission reduction during start-up where typically the highest emissions occur 3 Background and objectives (II) Therefore, a catalyst implementation into a stove may have several advantages: Light-off temperature of catalyst can be reached in short time high operation temperatures of the catalysts may support tar and soot reduction At high operation temperatures a better VOC reduction is expected Reduced risk of tar and soot deposits However, suitable materials for a high temperature application are needed as well as a higher pressure drop has to be considered. As usually primary measures are primarily applied as a tool to reduce emissions, a combination of primary and secondary measures may be a suitable approach for low emission wood stoves.

3 Based on this approach different high temperature catalysts have been integrated into a new low emission stove concept at different positions and their basic suitability has been evaluated. 4 The most common catalytic procedure to reduce emissions from stoves is the heterogeneous catalysis. At this type of catalysis the phase of the catalyst differs from that of the reactants: catalyst solid reactants gaseous The basic structure of solid catalysts consists of metals (most common is iron alloy) or ceramics ( aluminium oxide, zirconium oxide) Regarding the structure solid catalysts for emission reduction can be divided into: Packed beds Networks/ wire meshes Monoliths (honeycomb or foam structure) catalysts for wood stoves (I) Components of solid catalysts : Substrate: Carrier material for the washcoat and the active metal. The structure of the catalyst is defined by the material and production process of the substrate. Washcoat: To increase the surface of the catalyst a washcoat (powder suspension of metal oxides) is spread and dried on the substrate.

4 Substrate Washcoat Active metal Active metal: The surface is impregnated/coated with catalytically active components. Thereby the following main activities of the metals occur: Rh > Pd > Pt oxidation of CO Pt > Rh > Pd oxidation of VOC Rh > Pd > Pt reduction of NO At high operation temperatures also metals like Ni, Cu and Mg can achieve considerable conversion rates. catalysts for wood stoves (II) Methodology (I) Description of high temperature catalysts applied Based on an evaluation of catalysts available on the market and the experiences of test runs already performed two different types of high temperature catalysts have been investigated: Metal based honeycomb catalysts Active metals: Pt, Pd Catalytically coated foam ceramics Active metal: Pt The catalysts applied have been tested at different positions of the low emission stove: Metal based honeycomb catalysts installed at the outlet of the post combustion chamber mounting position I Foam ceramics with and without catalyst installed at the outlet of the main combustion chamber mounting position II 7 Specially adapted low emission logwood chimney stove with 2 flue gas pathways downstream the post combustion chamber Methodology (II) Description of the chimney stove applied Main combustion chamber Post combustion chamber Steel plate Window purge air Flue gas fan Primary air mounting position I honeycomb catalysts Air box mounting position II foam ceramics Dummy Catalyst 8 Methodology (III) Description of the test stand temperature combustion chamber Chimney O2, CO, CO2, OGC (Dummy) Chimney draught T before catalyst Pressure drop over catalyst TSP measurement Flue gas temperature measurement according to EN 13240 O2, CO, CO2, OGC CH4, (Catalyst)

5 temperature upstream foam ceramic O2, CO, CO2, OGC, CH4 Pressure drop over foam ceramic temperature downstream foam ceramic mounting position II - foam ceramic mounting position I - honeycomb catalyst 9 Methodology (IV) Test run procedure Performance of test runs with different high temperature catalysts at a low-emission logwood stove Long-term (2 or 3 weeks) operation of the stove with each catalyst Performance of dedicated testing campaigns with emission measurements One operation day consists of 8 successive batches (5 full load + 3 partial load) General operation conditions Constant draught of 12 Pa over the stove Test fuel: hardwood (beech) without bark, moisture content: 12 - 16 wt% Performance of gaseous and TSP emission measurements Gaseous emissions (CO, OGC, CH4, O2): continuous measurement from before ignition of batch 1 until the end of test run TSP emissions (according to VDI 2066): over the whole batch (from closing the door until opening it again) 10 Results of test runs performed (I) Honeycomb catalyst mounting position 1 11 Trends of CO emissions and CO reduction at the 1st day of operation Explanations: Emissions related to dry flue gas and 13 vol% O2 Trends of CO emissions and CO reduction at the 11th day of operation Batch 1 (ignition)Batch 2 Batch 3 Batch 4 Batch 5 Batch 6 (PL)Batch 7 (PL)Batch 8 (PL) 0 20 40 60 80 100 :4511:4512:4513:4514:4515:4516:4517:4518 :45 Reduction [%]CO [mg/Nm ]CO - CatalystCO - DummyCO - ReductionBatch 1 (ignition)Batch 2 Batch 3 Batch 4 Batch 5 Batch 6 PLBatch 7 PLBatch 8 PL 0 20 40 60 80 100 12002,0004,0006,0008,00010,00010:4011:40 12:4013:4014:4015:4016:4017:4018.

6 40 Reduction [%]CO [mg/Nm ]CO - CatalystCO - DummyCO - ReductionResults of test runs performed (II) Honeycomb catalyst mounting position 1 12 Trends of flue gas temperatures at the 1st day of operation Trends of flue gas temperatures at the 11th day of operation Batch 1 (ignition)Batch 2 Batch 3 Batch 4 Batch 5 Batch 6 PLBatch 7 PLBatch 8 PL10:4011:4012:4013:4014:4015:4016:4017: 4018:400100200300400500600700800900 temperatures [ C]T combustion chamberT catalyst inletT flue gasBatch 1 (ignition)Batch 2 Batch 3 Batch 4 Batch 5 Batch 6 (PL)Batch 7 (PL)Batch 8 (PL)10:4511:4512:4513:4514:4515:4516:451 7:4518:450100200300400500600700800900 temperatures [ c]T combustion chamberT catalyst inletT flue gasResults of test runs performed (III) Honeycomb catalyst mounting position 1 13 Influence of CH4 on OGC reduction Explanations: Results of test run at day 1; OGC reduction (green), non-methane OGC reduction (blue); % CH4 in OGC = (ppm CH4 / ppm OGC) * 100 CH4 is hardly converted by the catalyst Batch 3 Batch 4 Batch 5 0 10 20 30 40 50 60 70 80 90 100 12:40 13:10 13:40 14:10 14:40 15:10 15:40 16:10 OGC reduction [%] non-methane-OGC-reduction [%] CH4 in OGC [vol - %] Results of test runs performed (IV) Honeycomb catalyst mounting position 1 14 02468101214161820O2 - Dummy [vol% ]O2 - Catalyst [vol% ]Press.

7 Drop cat. [Pa]02040608010012002505007501,0001,2501 ,500CO - Dummy [mg/MJ]CO - Catalyst [mg/MJ]CO reduction [%]02468101214161820O2 - Dummy [vol% ]O2 - Catalyst [vol% ]Press. drop cat. [Pa]02040608010012002505007501,0001,2501 ,500CO - Dummy [mg/MJ]CO - Catalyst [mg/MJ]CO reduction [%]0204060801001200255075100125150 Day 1 Day 6 Day 11 Day 12 OGC - Dummy [mg/MJ]OGC - Catalyst [mg/MJ]OGC reduction [%]0204060801001200255075100125150 Day 1 Day 6 Day 11 Day 12 OGC - Dummy [mg/MJ]OGC - Catalyst [mg/MJ]OGC reduction [%]Nominal load Partial load Manual cleaning of the catalyst with compressed air after 11th day of operation Results of test runs performed (V) Honeycomb catalyst mounting position 1 Significant and partly very hard to remove fly ash deposits pressure drop increased Manual cleaning showed no effect on the emission reduction efficiencies Chemical analyses as well as SEM/EDX analyses clearly indicated that the catalyst has been de-activated by aerosol deposits (condensation of mainly K2SO4 and KCl), which have blocked the active centre of the catalysts 15 Catalyst before the test runs (view at outlet)

8 Catalyst after manual cleaning after 11 days of operation (view at inlet) Catalyst after 11 days of operation (view at inlet) Results of test runs performed (I) Foam ceramic mounting position 2 16 Trends of CO and OGC emissions at the 3rd day of operation Explanations: Emissions related to dry flue gas and 13 vol% O2 Trends of CO and OGC emissions at the 18th day of operation Batch1 (ignition)Batch2 Batch3 Batch4 Batch5 Batch6 (PL)Batch7 (PL)Batch8 (PL) 0 100 200 300 400 50001,0002,0003,0004,0005,00008:3009:301 0:3011:3012:3013:3014:3015:30 OGC [mg/Nm ]CO [mg/Nm ]CO flue gas [mg/Nm ]OGC flue gas [mg/Nm ]Batch1 (ignition)Batch2 Batch3 Batch4 Batch5 Batch6 (PL)Batch7 (PL)Batch8 (PL) 0 100 200 300 400 50001,0002,0003,0004,0005,00010:0011:001 2:0013:0014:0015:0016:0017:0018:00 OGC [mg/Nm ]CO [mg/Nm ]CO flue gas [mg/Nm ]OGC flue gas [mg/Nm ]Results of test runs performed (I) Foam ceramic mounting position 2 17 Trends of flue gas temperatures at the 3rd day of operation Trends of flue gas temperatures at the 18th day of operation Batch1 (ignition)Batch2 Batch3 Batch4 Batch5 Batch6 (PL)Batch7 (PL)Batch8 (PL)030060090008:3009:3010:3011:3012:301 3:3014:3015:30flue gas temperatureT upstream foam ceramic [ C]T downstream foam ceramic [ C]T flue gas [ C]Batch1 (ignition)Batch2 Batch3 Batch4 Batch5 Batch6 (PL)Batch7 (PL)Batch8 (PL)030060090010:0011:0012:0013:0014:001 5:0016:0017:0018:00flue gas temperatureT upstream foam ceramic [ C]T downstream foam ceramic [ C]T flue gas [ C]05101520253035O2 flue gas [vol% ]Press.

9 Drop foam ceramic [Pa]025507510002505007501,000CO flue gas [mg/MJ]CO reduction %05101520253035O2 flue gas [vol% ]Press. drop foam ceramic [Pa]02040608010002505007501,000CO flue gas [mg/MJ]CO reduction %020406080100020406080100 Day 3 Day 11 Day 18without foam ceramicOGC flue gas [mg/MJ]OGC reduction %020406080100020406080100 Day 3 Day 11 Day 18without foam ceramicOGC flue gas [mg/MJ]OGC reduction %0510152025 Day 3 Day 11 Day 18without foam ceramicTSP [mg/MJ]0510152025 Day 3 Day 11 Day 18without foam ceramicTSP [mg/MJ]Results of test runs performed (II) Foam ceramic mounting position 2 18 Nominal load Partial load Manual cleaning of the catalyst with compressed air after 11th day of operation Results of test runs performed (III) Foam ceramic mounting position 2 Some fly ash deposits on the surface of the foam ceramic slight increase of pressure drop By manual cleaning most of the fly ash deposits could be removed and the pressure drop over the foam ceramic could be reduced again Manual cleaning showed no effect on the emission reduction efficiencies 19 Foam ceramic before the test runs Foam ceramic after 18 days of operation Foam ceramic after 11 days of operation Conclusions and recommendations (I) The implementation of a high temperature catalyst at the outlet of the post combustion chamber ( temperature range of about 500 C) is not recommended as tests showed unstable reduction efficiencies.

10 Decreasing reduction efficiencies over time can most likely be attributed to catalyst de-activation as a consequence of blocking of active centers caused by aerosol condensation. high temperature catalysts , which are mounted at the outlet of the main combustion chamber ( temperature range 600 - 800 C) showed sufficiently high emission reduction efficiencies regarding CO (69 73%) and OGC (27 38%) and seem basically to be suitable for logwood stoves. However, the emission reduction efficiency decreased for the catalysts over the testing period of about 100 hours of operation and manual cleaning showed no positive effect 20 Conclusions and recommendations (II) Tests over a whole heating period would be needed to be able to evaluate the long-term performance of catalysts in wood stoves as well as the possible need of cleaning. Furthermore, catalysts need enough surface to achieve a sufficient reduction efficiency. This is usually provided by narrow channels which cause a certain pressure drop.


Related search queries